In a semiconductor device manufacturing process, a target substrate to be processed, i.e., a semiconductor wafer (hereinafter, simply referred to as a wafer), is subjected to various heat treatments such as a film forming process, an oxidation/diffusion process, a quality modification process, and an annealing process. Especially, in the annealing process after ion implantation, it is required to increase and decrease the temperature rapidly so as to minimize the diffusion, in response to the demand for the high speed and high integration of semiconductor device. There has been disclosed an annealing apparatus capable of increasing and decreasing the temperature rapidly, the annealing apparatus employing light emitting diodes (LED) as a heating source (see, e.g., Japanese Patent Application Publication No. 2005-536045).
In the case of employing LEDs as the heating source of the annealing apparatus, it is necessary to generate a lot of energy to increase the temperature rapidly and, thus, it is required to mount the LEDs with high density.
However, it is known that the emission amount of an LED is reduced as the temperature of the LED is increased by the heat radiated from the LED. Moreover, when LEDs are mounted with high density, if the LEDs are significantly affected by the heat radiated from themselves (e.g., the remaining portion of the supplied energy which is not emitted as lights), it becomes difficult to obtain sufficient emission amount from the LEDs. For that reason, it is suggested to cool the LEDs so as to suppress the reduction of the emission amount caused by the heat radiated from the LEDs. However, a large scale cooling device is required to effectively cool the high-density mounted LEDs and, resultantly, the maintenance thereof becomes an issue.
Further, lights are emitted from side surfaces of the LED as well as a facing surface thereof that faces a target wafer to be heated. A side length of the LED is in the range of about 0.3 to 1 mm, and a thickness thereof is in the range of about 0.2 mm. In addition, the area of 4 side surfaces thereof is wider than that of the facing surface thereof. Accordingly, the efficiency of obtaining lights may be reduced.